Method of producing soft magnetic powder

Abstract

Disclosed is a method of producing a soft magnetic powder including spraying gas or water into a pure iron bath to prepare a pure iron powder, surface-treating the pure iron powder by milling to increase surface stress of the pure iron powder and make the pure iron powder spherical, and subjecting the surface-treated pure iron powder to reducing thermal treatment to grow surface crystal grains of the pure iron powder and to prepare a soft magnetic powder.

What is claimed is: 
     
         1 . A method of producing a soft magnetic powder comprising:
 spraying gas or water into a pure iron bath to prepare a pure iron powder;   surface-treating the pure iron powder by milling to increase surface stress of the pure iron powder and make the pure iron powder spherical; and   subjecting the surface-treated pure iron powder to reducing thermal treatment to grow surface crystal grains of the pure iron powder and to prepare the soft magnetic powder.   
     
     
         2 . The method according to  claim 1 , wherein the milling is carried out by ball-milling using a ball with a diameter of 2.5 to 3.5 mm. 
     
     
         3 . The method according to  claim 2 , wherein the milling is carried out by milling in a weight ratio of the ball to the pure iron powder of 7:1 to 10:1 for 5 to 7 hours for surface-treatment. 
     
     
         4 . The method according to  claim 3 , wherein, during the milling, the surface-treated pure iron powder has an apparent density of 3.6 g/cc or more and a flow rate of 2.8 g/s or more. 
     
     
         5 . The method according to  claim 3 , wherein, during the milling, the surface-treated pure iron powder has an apparent density of 3.6 g/cc or more and a flow time of 18 s/50 g or less. 
     
     
         6 . The method according to  claim 1 , wherein the thermal treatment is carried out under an inert atmosphere at a temperature of 480 to 530° C. 
     
     
         7 . The method according to  claim 1 , wherein the soft magnetic powder has a saturation flux density of 1.55 T or more and a core loss of 45 W/kg or less under conditions of 400 Hz and 1.0 T.